Electrochemical Ring Contraction Tandem Sulfonation of Saturated Six-Membered Azacycles to Sulfonated Pyrrolidines

Despite remarkable progress in the peripheral editing of saturated N-heterocycles, skeletal editing via ring contraction remains one of the most intriguing yet formidable challenges in this field. Herein, we report a novel ring contraction tandem sulfonation of saturated azacycle N-oxides with sulfonyl hydrazides or sodium sulfinates to access sulfonated pyrrolidine derivatives enabled by an electrochemical redox cascade. A series of functionalized products was generally obtained in moderate to good yields under mild conditions. Moreover, the utility of this approach has been demonstrated by the gram-scale preparation and the synthesis of pharmaceutical molecules.